Construction Board

ABSTRACT

The present application provides wood fiberboard comprising wood fibers bound together with a binder polymer resin that imparts additional strength and moisture resistance. As well, the fiberboard incorporates a thermal fire suppressing inorganic expandable flake graphite and sodium silicate component to render the fiberboard to be non-combustible and fire resistant. As well, a manufacturing process for adding the inorganic graphite and polymer resin binder into the fiberboard and applying the silicate onto the fiberboard is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser. No. 15/557,751 filed Sep. 12, 2017, which is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/CA2016/050274 filed on Mar. 11, 2016 and published in English as WO 2016/145517 A1 on Sep. 22, 2016. This application claims the benefit of priority from U.S. Provisional Application No. 62/132,915 filed Mar. 13, 2015. The entire disclosures of all of the above applications are incorporated herein by reference.

FIELD

The present disclosure relates to construction boards, in particular fiberboards.

BACKGROUND

Fiberboard (cellulosic fiber)—structural and decorative—is a fibrous-felted, homogeneous panel made from ligno-cellulosic fibers—usually wood—which has a density of less than 31 lb/ft3 (497 kg/m3), but more than 10 lb/ft3 (160 kg/m3). Fiberboard is characterized by an integral bond which is produced by interfelting the fibers, but which has not been consolidated under heat and pressure as a separate stage in manufacture. Other materials may be added to fiberboard during manufacture to improve certain properties of the produced panel such as well known waxes to provide moisture resistance and well known plant derived starches for fiber bonding to impart degrees of strength. It is also well known in the long history of the manufacture of wood produced fiberboards that many sectors of building related projects are well suited for wood fiber boards that impart added thermal insulation qualities, sound suppression benefits, as well as providing for an economical construction cover board. For example, fiberboards are easy and light to install and may be used as interior wallboards or as exterior sheathing. Although there have been numerous advances in the history of fiberboard production in these areas there are some serious shortcomings that are inherent in the present state of the art. For example, the following are issues of concern with current construction boards and fiberboards:

1) Wood fiberboards are flammable in nature and must not be left exposed under existing building code requirements; 2) Wood Fiberboards are susceptible to moisture degradation due to mold and organic decay and must be treated to meet existing building code requirements; 3) Wood fiberboards are generally weak in strength as compared to other construction cover boards where structural stability is required; and 4) Wood fiberboards are not smooth in composition and readily release fibers when handled or lightly abraded during standard installation procedures and are not considered as acceptable candidates for architectural finishes such as paint.

Over the past several years, alternative materials to commodity grade fiberboards have become available, including gypsum boards, oriented strand boards (OSB), expanded polystyrene (EPS) and polyisocyanurate boards (Polyiso). Due to these alternative materials, demand for fiberboard has decreased. For example, production capacity of fiberboard in North America has been reduced by 37.5% over the last 5 years. However, these alternative materials have their own challenges and are less eco-friendly than fiberboard.

SUMMARY

The present invention relates to a wood fiberboard comprising wood fibers bound together with a binder polymer resin that imparts additional strength, moisture resistance and incorporating a thermal fire suppressing expandable flake inorganic graphite and sodium silicate component to render the fiberboard to be non-combustible.

The invention here described discloses a method of substantially improving the fire resistance properties of a Fiberboard (Cellulosic fiber) homogenous panel by the admixture during the manufacturing process of certain known intumescent and binding materials in such a way that a significant and unexpected improvement in the properties of the fiberboard composition may be achieved. In fact the unexpected improvements rival thermal resistance and fire protection properties that are only generally achieved by well known inorganic construction boards such as Dens glass, gypsum and concrete wallboards (Drywall)

In order to address the shortcomings addressed in the current state of art mentioned above, research was carried out to develop a process where the admixing of preferred components could be carried out in the standard manufacturing methods currently considered as the state of the art in the manufacture of said fiberboards. The research investigated:

(a) A water borne polymer binder that can be added to the present manufacturing process so as to impart additional strength as well as impart water resistance. This polymer binder would be implemented in a similar manner and in a similar position as the existing current art of using the aforementioned waxes and starches. (b) A known intumescent and/or fire retardant that would also be compatible to the existing current art of fiberboard production. (c) A preferred method of surface treatment to the face of the fiberboard so as provide for a smooth and acceptable finish that incorporated the use of an inorganic sodium silicate to increase strength and fire resistance.

In the present application, the terms “fiberboard” and “construction board” may be used interchangeably.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to the following drawings:

FIG. 1 is a block diagram illustrating a manufacturing system for producing a construction board product according to one embodiment of the present application;

FIG. 2 is a block diagram illustrating a continuation of the manufacturing system for producing the construction board product according to the one embodiment of the present application;

FIG. 3 is a graph illustrating the mean furnace temperature during a full wall burn test of a sample construction board having 30% of graphite by weight according to an embodiment of the present application;

FIG. 4 is a graph illustrating the mean furnace temperature during a full wall burn test of a sample construction board having 15% of graphite by weight according to an embodiment of the present application;

FIG. 5 is a graph illustrating the unexposed face maximum temperature during a full wall burn test of a sample of construction board of the present application;

FIG. 6 is a graph illustrating the unexposed face average temperature during a full wall burn test of a sample of construction board of the present application;

FIG. 7 is a graph illustrating the furnace pressure during a full wall burn test of a sample of construction board of the present application;

FIG. 8 is a graph illustrating the surface temperature of a conventional fiberboard subjected to a heat test;

FIG. 9 is a graph illustrating the surface temperature of a fiberboard having a silicate coating subjected to a heat test;

FIG. 10 is a graph illustrating the surface temperature of a fiberboard comprising graphite according an embodiment of the present application subjected to a heat test; and

FIG. 11 is a graph illustrating the surface temperature of a fiberboard comprising graphite according an embodiment of the present application subjected to a heat test.

DETAILED DESCRIPTION

In a first aspect of the present disclosure, a fiberboard composition is provided comprising a plurality of ligno-cellulosic fibers and an inorganic expandable graphite in an amount suitable for providing fire resistance. The ligno-cellulosic fibers may be wood-based, cardboard, or any other organic ligno-cellulosic fiber known to one skilled in the art. The inorganic expandable graphite forming part of the fiberboard composition provides fire-resistance properties. The inorganic expandable graphite may not expand at temperatures less than about 240° C. In some embodiments, the inorganice expandable graphite may not expand at temperatures less than about 220° C. A suitable inorganic expandable graphite is produced by Asbury Carbons and sold under the product ID Expandable Graphic Grade 1722HT (previously product number RD18702 HT). In one embodiment, the fiberboard comprises between 15% to 30% of graphite by weight. In other embodiments, the content of graphite in the fiberboard may be larger, for example up to 60% of graphite by weight. The graphite in the fiberboard improves the fire resistance properties of the fiberboard. For example, the fiberboards of the present application meet and exceed fire-resistance ratings according to Canadian and International standards. Due to the fire-resistance properties of the fiberboard, it may be used in various industries and applications, for example in interior home and building construction as well as for exterior sheathing of structures.

The fiberboard composition may further comprise a waterborne polymer binder resin in an amount suitable for providing water resistance. Various types of waterborne polymer binder resins may be used. For example, this waterborne polymer binder resin may be selected from the group consisting of: latex, natural rubber, gutta-percha, styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene, polybutadiene, polychloroprenes, organic polysulphides, butyl rubber, halogenated butyl rubber, chlorinated polyethelene, chlorosulfanated polyethylene, ethylene-propoylene rubber, butadiene acrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, and all acrylic polymers, or other waterborne polymer binder resins known to one skilled in the art. The use of the polymer binder resin instead of a starch binder provides a fiberboard with increased strength properties. Due to the increased strength of the fiberboard product of the present application, the fiberboard products may be used in various industries for multiple applications, including roofing systems, exterior siding, and sound proofing.

The fiberboard composition may further comprise a silicate for enhancing fire resistance. This silicate may be around 10% water-based and may be selected from the group consisting of sodium silicate and potassium silicate.

It is here disclosed a novel process that allows the admixing of certain known polymer binder formulations as well as the inclusion of known inorganic intumescent graphite particles in the present state of the art in the manufacturing of Fiberboard (Cellulosic).

While various types of polymeric binders were found to be effective in providing the required strength and water resistance that included a wide range of latexes well known to the art that include dispersions of natural rubber, gutta-percha, styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene, polybutadiene, polychloroprenes, organic polysulphides, butyl rubber, halogenated butyl rubber, chlorinated polyethelene, chlorosulfanated polyethylene, ethylene-propoyl ene rubber, butadi ene acrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, all acrylic polymers and the like. For properties needed to achieve the desired requirements, the preferred binder was found to be included in the class of elastomeric styrenated acrylic in which the proportion of styrene to methyl acrylic acid between 10/90 and 20/80 and the glass transition temperature of +5° C. or higher as produced by Ona Polymers of Garland Texas USA. The ability to increase strength and water resistance was achieved by direct in line addition of approx: 2-3 gals per minute into the pulp slurry during the manufacture of the fiberboard as it was being formed just ahead of the forming line presses.

While various types of known fire retardants and inorganic intumescents were trialed including APP, diammonium salts, monoamonium salts, borates, and boric acid, the preferred inorganic intumescents was discovered to be expandable graphite as produced by Asbury Carbons and Sodium Silicate as produced by PQ Corporation which could be readily dispersed through the existing and current art of fiberboard production.

The wood fiber used in the present method is acquired through conventional methods of processing recycled wood. For example, recycled wood products may be cut up into wood chips and processed using conventional processes to remove any foreign materials and other impurities. Such a conventional process may include use of a belt and magnet conveyor to remove any metallic foreign materials from the wood chips. Next, the wood chips may be treated using conventional processes for cleaning and treating the wood chips.

As shown in FIG. 1, there is provided one embodiment of a manufacturing system 100 for producing the construction board of the present application. In this embodiment, the system 100 includes a machine chest 102, a constant level box 104 and a head box 108. The machine chest 102 contains a mixture of the processed and/or treated wood fiber and water (for example, also referred to herein as wood pulp slurry). During manufacturing graphite is added into the machine chest 102 at a substantially constant rate. This allows the graphite to evenly mix with the wood fiber pulp and water mixture prior to the graphite wood fiber mixture entering the head box 108. For example, the graphite may be introduced into the machine chest 102 at a constant rate of ten (10) pounds of graphite per minute. The graphite may be added into the machine chest 102 manually or by some automated system or component (not shown). In alternative embodiments, the graphite may be introduced at a different location during the manufacturing process, such as at the head box 108 or prior to the machine chest 102.

The graphite wood fiber mixture previously combined in the machine chest 102 is moved via the constant level box 104 using a pump 106 into the head box 108. The constant level box 104 recirculates any overflow back to the machine chest 102. In some embodiments, a coloring agent is added to the graphite wood fiber mixture using a coloration device 103 such that the finished product will have a particular color. As well, water is circulated into the head box 108 by a dilution device 105 to provide a high water content mixture.

The graphite wood fiber mixture is then evenly distributed onto the formation table 110, which has a flat wire mesh surface. At the entry point of the formation table 110 (and after mixing with water in the head box 108), the graphite wood fiber mixture is approximately comprised of 99% water and 1% of combined wood fiber and graphite. The graphite wood fiber mixture is moved along the formation table 110 towards a plurality of rollers 118. Prior to reaching the plurality of rollers 118, water in the graphite wood fiber mixture is filtered out of the mixture through the wire mesh on the formation table 110 and into the water canal 116. As well, water may be further removed from the graphite wood fiber mixture using a low vacuum 112 and a high vacuum 114 along the formation table 110. After the removal of the water using the low and high vacuums 112, 114, the graphite wood fiber mixture is approximately comprised of 70% water and 30% of combined wood fiber and graphite. The graphite wood fiber mixture is then passed through a plurality of rollers 118 which flatten the mixture to a predetermined thickness. An overhead vacuum system 111 removes moisture and water from the graphite wood fiber mixture while it is being passed along the formation table and while it is being flattened. As well, during the flattening step, further water is removed from the graphite wood fiber mixture, the water falling into the water canal 116. After flattening, the mixture is now formed into a semi-rigid board on the formation table 110. An optional coating may be applied to the semi-rigid board at this stage from coating shower system 126. The semi-rigid pre-fiberboard is cut into predetermined sized pieces by the cross-cutter 120 and then is sent to a dryer system 200 for drying and hardening. At this stage, the semi-rigid pre-fiberboard is approximately comprised of 48% water and 52% of combined wood fiber and graphite. Any excess graphite wood fiber mixture falls into a pulper 122 and is stored in a reserve chest 123.

FIG. 2 illustrates the dryer system 200 as part of the overall manufacturing system of the fiberboard shown in FIG. 1, according to the one embodiment of the invention. The semi-rigid board continues onto one or more conveyors 202 into one or more dryers 204. The dryers 204 operate to remove the majority of the remaining water that is in the semi-rigid fiberboard. The dryers 204 remove a significant amount of water such that the dried fiberboard leaving the dryers 204 is approximately comprised of 5% water and 95% of combined wood fiber and graphite. The dried fiberboard exits the dryers 204 onto one or more conveyors 205 and may be cut into predetermined sized pieces by one or more saws 206. The fiberboard may be cut in any size of board. After the dried fiberboard has been cut, the fiberboard proceeds onto a conveyor 208 to receive final treatments. For example, the surface of the fiberboard may be smoothed by a calender 210, the surface of the fiberboard may receive a polymer coating applied by a coating device 212 and the surface of the fiberboard may be laminated by a lamination device 214. After receiving the one or more final treatments, the finished fiberboard product may be stored. The finished fiberboard may be cut into boards having generally the dimensions 4 feet×8 feet×½ feet. The fiberboard may be cut into any size and the thickness of the finished fiberboard may vary depending on the intended end use application.

During the trials there were a number of obstacles that needed to be overcome.

1. Polymer Binder

(a) Although a waterborne polymer emulsion was compatible with existing manufacturing methods during the process it was found that the surfactants in the polymers had to be re-worked and cross linked as they were impacting water resistance due to their very nature of being hydrophilic. A new proprietary surfactant had to be added to the polymer binder with a cross linking agent WB31B (metal complex) as produced by Federal Process Corp that reacts only after the formulation soaks into the wood fiber and the water evaporates. Cross linking the surfactant destroys its ability to attract water and preserves depth of penetration better than solvent-based systems. (b) The polymer binder had to be adjusted to a cationic ph of 6 or less so as bind to the cellulosic fiber as the fiber carried an anionic charge to enhance attraction. (c) The polymer binder may be added to the machine chest 102 or may be added to the head box 108, for mixing with the wood fiber slurry. As well, the polymer binder may be added at another point during the manufacturing process. The use of the polymer binder rather than conventional binders (e.g. starch) results in a stronger fiberboard product. Due to the increased strength properties of the fiberboard of the present application, it may be used in various industries and for various applications that conventional fiberboard could not be used, for example for roofing applications which require a certain level of structural strength, for example, to permit walking on top of fiberboard. (d) The percentage of the polymer binder in the fiberboard was trialed approximately between 0% to 15%.

TABLE 1.1 TC12-xxxx (ID#) 173G 174I 174H 17OA 174J Binder Starch Starch Starch polymer polymer % solids of Binder N/A N/A N/A 55% 55% Weight of Binder 2.07% 2.12% 2.02% 1.91% 1.93% Wood Fiber 28.05% 27.80% 27.25% 28.08% 27.92% Water 69.88% 68.98% 67.02% 69.83% 68.73% Crosslink-WB31B 0.00% 0.00% 0.00% 0.18% 0.18% Wax 0.00% 1.09% 3.70% 0.00% 1.24% Total 100.00% 100.00% 100.00% 100.00% 100.00% Wt. Before water (g)  8.5640 (g)  7.9883 (g)  8.4619 (g)   8.4225 (g)%  8.0680 (g) Wt. After 2 Hr (g) 14.5257 (g) 12.6892 (g) 12.3866 (g) 11.3183 (g) 10.2342 (g) Absorption 2 Hr (%) 69.61% 58.55% 46.38% 34.38% 26.85% Wt. Before water (g)  8.3347 (g)  8.3696 (g)  8.5919 (g)  8.8394 (g)  8.1127 (g) Wt. After 4 Hr (g) 34.9321 (g) 14.8635 (g) 14.7384 (g) 11.9293 (g) 10.8069 (g) Absorption 4 Hr (%) 319.10% 77.59% 71.54% 34.96% 33.21%

Table 1.1 illustrates a comparison between conventional fiberboards having starch as a binder and fiberboards of the present application which utilize polymer as a binder. The example fiberboards 173G, 174I and 174H each utilized starch as a binder. Starch is a highly combustible material. Fiberboards 173G, 174I and 174H have generally the same percentages of wood fiber, water and weight of the starch binder. The characteristics of fiberboards 173G, 174I and 174H differ in the percentage of wax used, with 173G having 0%, 174I has 1.09% and 174H having 3.70%. The use of wax in the fiberboards decreases the water absorption percentage after 2 hours and after 4 hours, with the highest amount of wax 3.70% in fiberboard 174H providing the lowest water absorption rates.

As shown in Table 1.1, Fiberboards 170A and 174J of the present application utilize the above-described polymer as a binder. The fiberboards 170A and 174J have generally the same percentages of solids of the polymer binder, wood fiber, crosslink-WB31B and water, and generally the same weight of the polymer binder. The characteristics of the fiberboards 170A and 174J differ in the percentage of wax used, with 170A having 0% and 174J having 1.24%.

When comparing conventional fiberboard 173G with the fiberboard 170A according to the present application, where both have no wax component, it is shown that the water absorption percentage (2 hours and 4 hours) is reduced significantly when the binder of the fiberboard is the polymer binder having the new proprietary crosslinking agent WB31B of the present application. For example, the 4 hour water absorption percentage of the fiberboard 170A of the present application is 34.96% in contrast to the conventional fiberboard 173G which has a 4 hour water absorption percentage of 319.10%.

Fiberboard 174J of the present application differs from fiberboard 170A in that it contains 1.24% of wax. The introduction of the wax does not provide a significant decrease in water absorption percentages, as the 4 hour water absorption percentage of the fiberboard 174JA of the present application is 33.21% and the 4 hour water absorption percentage of the fiberboard 170A (without wax) of the present application is 34.96%.

Conventional fiberboards 173G, 174I and 174H are made with a starch binder and include a wax component in order to reduce percentages of water absorption. However, one problem with using starch and wax in fiberboards is that these materials are highly flammable. In the present application, the fiberboards are manufactured without starch and without wax, making them less flammable than conventional fiberboards. Instead of a starch binder, the fiberboards of the present application manufactured with a polymer binding, which results in decreased water absorption percentages than the conventional starch binder based fiberboards.

2. Expandable Graphite

(a) Expandable graphite is known as an intercalation compound, the expansion factor and ability to expand is determined by temperature gradients. It is thus desirable that the expansion occur rapidly once the material reaches a certain critical value. Most commonly the temperature at which such expansion commences is within the range of 150° C. to 220° C. The production of Fiberboard requires travel through ovens 204 (FIG. 2) in the drying process where temperatures exceed 240° C. It was imperative that we have the manufacturer of the graphite produce graphite with higher temperature limits. Asbury Carbons a world leader in carbon mining was able to formulate a new high temperature reactive graphite that met our requirements and it has been commercially branded as Expandable Graphic Grade 1722HT (previously identified as RD18702 HT). Accordingly, with the use of the expandable graphic having higher temperature limits, particularly Grade 1722HT, this obstacle was overcome. Table 1.2 shows the typical properties of expandable graphite at different grade levels as indicated and sold by Asbury Carbons. As previously discussed, for the present application, the preferred grade of expandable graphite is 1722HT as the onset temperature is very high (220-230° C.); and will work with furnace temperatures in the 240° C. range.

TABLE 1.2 Asbury Carbons - Typical Properties Expandable Graphite Nominal Size Carbon Moisture Sulfur Expansion Ratio Onset Temp. Grade (μm) (%) (%) (%) (cc/g) pH range (° C.) 3772 >300 ≥98 0.9 3.1 300:1 5-10 180-200 1721 >300 ≥98 0.9 3.5 300:1 1-6  180-200 3721 >300 ≥95 0.9 3.5 290:1 5-10 180-200 1722 >300 ≥95 0.9 3.5 290:1 1-6  180-200 3335 >300 ≥85 0.9 3.2 270:1 5-10 180-200 3577 >300 ≥85 0.9 3.4 270:1 1-6  180-200 3570 >180 ≥80 0.8 3.1 230:1 5-10 150-170 1395 >180 ≥80 0.8 3.5 230:1 1-6  150-170 3558 >180 ≥99 0.8 3.1 210:1 5-10 180-200 3626 >75 ≥80 0.6 3.0 160:1 5-10 150-170 3494 >75 ≥80 0.9 2.9  90:1 1-6  160-180 3538 <75 ≥80 1.4 2.6  60:1 5-10 200-225 1722HT >300 ≥95 1.6 5.0 220:1 1-6  220-230 (b) As the expandable graphite is a solid and not a liquid, this posed a problem as to how and where to insert the required flow so as to have correct particle distribution throughout the mass of the fiberboard panel. This obstacle was overcome after trialing numerous entry areas. The preferred entry point was identified at the existing head box 108 that in fiberboard production provides the distribution of wood fiber slurry by high volume agitation evenly throughout the main forming line. By adding the graphite at the rate of 10 lbs per minute at this location very uniform particle distribution was recorded. In some embodiments, the graphite is added to the machine chest 102 at a constant rate, prior to the head box 108. The introduction of graphite during the fiberboard manufacturing process as described herein results in a fiberboard product having improved fire resistance properties.

3. Surface Treatment

The surface treatment of the face of the boards is realized by subjecting the finished board as it came out of the dryers 204 to a surface coat of sodium silicates (case trials were done with both sodium and potassium silicates and sodium due to its relatively inexpensive cost was chosen as the preferred method.) The surface treatment was optimized using a spray coat of a 10% water based solution (higher and lower concentrations in the range of 5% to 100% were trialed but the optimum was 10%) of inorganic sodium silicate which quickly penetrated the surface of the fiberboard and then was sent into a calender press roller 210 to provide a suitable smooth profile for paint application. In some embodiments, the surface treatment is performed by a coating device 212 after the fiberboard is sent into the calender press roller 210, as shown in FIG. 2. The application of the sodium silicate was enhanced by the addition of a high heat (450 F-500 F) pressure compression roller that not only provided for a smooth surface but in doing so set the sodium silicate due to the high temperature flash drying of the water carrier that resulted in a smooth glass like appearance that provided an additional fire resistance quality that is well known in this particular chemistry of silicates otherwise known as waterglass.

To exemplify the fire resistant characteristics of the fiberboard of the present application, full wall burn tests were performed. For these tests, fiberboard made with natural pulp and comprising the graphite, polymer resin binder and the silicate coating was used. A first batch of the fiberboard was produced with a graphite content of 15% by weight (for example, during manufacturing the graphite may be added at a rate of 5 lbs of graphite per minute) and a second batch of fiberboard was produced with a graphite content of 30% by weight (for example, during manufacturing the graphite may be added a rate of 10 lbs of graphite per minute).

FIG. 3 is a graph of the mean furnace temperature during the CAN ULC S101-14 full wall test of fiberboard from the second batch having a graphite content of 30% by weight. The x-axis of FIG. 3 represents the temperature of the furnace in Fahrenheit and the y-axis represents the length of time in minutes the fiberboard burns until it reaches a failure state. For the purposes of the full wall burn test, a failure state of the fiberboard is when the fiberboard reaches a thermal loss value that exceeds ASTM fireproofing standards. As shown in FIG. 3, two thermal losses occur after 35 minutes and after 40 minutes. Conventional fiberboards subjected to a similar full wall burn test would reach a thermal loss within 5 minutes. Accordingly, the fiberboard of the present application provides superior fireproofing qualities compared to conventional fiberboard. This improved fireproofing characteristic of the fiberboard of the present application is in part a result of the graphite added to the fiberboard during manufacturing.

FIG. 4 is a graph of the CAN ULC S101-14 mean furnace temperature during the full wall test of fiberboard from the first batch having a graphite content of 15% by weight. As shown, a thermal loss occurs on the graph between 25 and 30 minutes. Accordingly, when comparing the full wall burn test results of the first batch of fiberboard having 15% graphite by weight with the second batch of fiberboard having 30% graphite by weight, it is shown that the increased amount of graphite in the fiberboard resulted in an increase in time before a thermal loss event occurs, thereby improving the fireproofing characteristics of the fiberboard.

FIG. 5 is a graph illustrating the unexposed face maximum temperature during a CAN ULC S101-14 full wall burn test of a sample of construction board of the present application;

FIG. 6 is a graph illustrating the unexposed face average temperature during a CAN ULC S101-14 full wall burn test of a sample of construction board of the present application;

FIG. 7 is a graph illustrating the furnace pressure during a CAN ULC S101-14 full wall burn test of a sample of construction board of the present application.

The fiberboard (Cellulosic fiber) of the present application is rendered non-combustible due to the inclusion in its composition of a new high temperature activated expandable graphite.

As well, the fiberboard (Cellulosic fiber) of the present application has improved strength characteristics and water resistance properties due to the inclusion of polymer binders in its composition.

Also, the fiberboard (Cellulosic fiber) of the present application has a sodium silicate (waterglass) surface treatment and compressed profile that results in a smooth and paint ready surface with inherent fire resistant properties.

Thermal testing was conducted on sample fiberboards to illustrate the effects that the silicate and graphite, alone and in combination, have on the thermal resistant properties of the fiberboard of the present application. As a baseline, a thermal test was conducted on a standard conventional fiberboard. For each of the thermal tests, the furnace temperature was maintained at an approximate temperature of 1500° F. On the graphs in FIGS. 8 to 11, where the unexposed surface temperature of the board is shown to surpass the furnace temperature is an indication of a thermal loss event, which may considered as a failure point of the fiberboard that is being subjected to heat.

FIG. 8 illustrates the results of such the thermal test on a conventional fiberboard. As shown, the unexposed surface temperature of a conventional fiberboard rapidly rises to just over 1400° F. and reaches a failure state in less than approximately 2 minutes.

FIG. 9 illustrates the results of the thermal test on a fiberboard having a silicate coating. As previously discussed, a silicate coating provides fire-resistant properties to a fiberboard. In FIG. 9, the unexposed surface temperature rises to approximately only 400° F. after 30 minutes of exposure, despite the furnace temperature being approximately 1500° F. The fiberboard having the silicate coating reaches a failure state at approximately between 35 and 40 minutes. Accordingly, the silicate coating on the fiberboard provides improved thermal resistance when compared with the heat test results of the conventional fiberboard of FIG. 8 which reached a failure state within 2 minutes under the same furnace temperature conditions.

FIG. 10 illustrates the results of the thermal test on a fiberboard comprising a predetermined percentage of graphite, according to the present application. As previously discussed, the introduction of graphite during the fiberboard manufacturing process, as provided in the present application, improves the fire resistant properties of the fiberboard. In FIG. 10, the unexposed surface temperature rises to approximately only 400° F. after about 35 minutes of exposure, despite the furnace temperature being approximately 1500° F. The fiberboard comprising the graphite reaches a failure state at approximately between 40 and 50 minutes. Accordingly, the fiberboard comprising graphite provides improved thermal resistance when compared with the heat test results of the conventional fiberboard of FIG. 8 which reached a failure state within 2 minutes under the same furnace temperature conditions.

FIG. 11 illustrates the results of the thermal test on a fiberboard comprising a predetermined percentage of graphite and having a silicate coating, according to the present application. In FIG. 11, the unexposed surface temperature rises to approximately only 400° F. after about 45 minutes of exposure, despite the furnace temperature being approximately 1500° F. The fiberboard comprising the graphite and having the silicate coating reaches a failure state at approximately 50 to 55 minutes. Accordingly, the combination of the fiberboard comprising graphite and having a silicate coating provides the greatest level of thermal resistance relative to the examples provided in FIGS. 9 (fiberboard having silicate coating only) and 10 (e.g. fiberboard comprised of graphite only). As well, the combination of the fiberboard comprising graphite and having a silicate coating provides significant improvement of thermal resistance (e.g. failure after 50 minutes of heat exposure) when compared with the heat test results of the conventional fiberboard of FIG. 8 which reached a failure state within 2 minutes under the same furnace temperature conditions.

Furthermore, various tests (for example, to identify thermal conductivity, water absorptiveness) were performed to compare the standard specifications of gypsum board (for example, according to ASTM 1.1.1 standard) to samples of the fiberboard of the present application. For these tests, the fiberboard samples of the present application has a thickness of approximately ⅝ inches. As well, the tests were performed on samples of ⅝″ gypsum boards having water-repellent surfaces.

Tables 2.1 and 2.2 show results of thermal conductivity tests performed in accordance with the ASTM C518 standard. In Tables 2.1, the thermal conductivity of the gypsum boards is shown. The RSI value for thermal resistance is 0.08 Cm²/W for the gypsum board, the heat flow rate in the measured area is 12.45 W, and the thermal conductivity rating is R=0.48.

TABLE 2.1 Thermal conductivity on 5/8″ gypsum boards with water-repellent surfaces (According to Standard ASTM C518) Thermal Heat flow rate resistance Thermal in the metered K at 1″ resistance Dry Sample ΔX_(Theoretical) ΔX area (Q) ΔT BTU · po/ ° F. · pi² · h/ ° F. · pi² · h/ RSI weight Density — in (°) in (°) W ° F. ° F. · pi² · h BTU BTU ° C. · m³/W g lbs/pi³ ⅝″ 0.625 0.620 12.45 2.04 1.305 0.766 0.48 0.08 1036.08 44.28 gypsum

In Table 2.2, the thermal conductivity properties of sample fiberboards of the present application are shown (for example, the fiberboard has the proprietary name “Starboard”). For the fiberboard #7 having the characteristics and properties of the present application, the RSI value for thermal resistance is 0.29 Cm²/W and the heat flow rate in the measured area is 5.53 W. The other tested fiberboard #8 of the present application as tested had a similar RSI and heat flow rate as fiberboard #7. The thermal conductivity rating of fiberboard #7 is R=1.63 and of fiberboard #8 is R=1.59.

TABLE 2.2 Thermal conductivity on ⅝″ MSL fireproof and calendered fiberboard of the present application (According to Standard ASTM C518) Thermal Heat flow rate resistance Thermal in the metered K at 1° resistance Dry Sample ΔX_(Thermal) ΔX area (Q) ΔT BTU · po/ ° F. · pi² · h/ ° F. · pi² · h/ RSI weight Density — in (°) in (°) W ° F. ° F. · pi² · h BTU BTU ° C. · m³/W g lbs/pi³ Starboard #7 0.625 0.810 5.53 2.97 0.375 2.667 1.63 0.29 484.36 21.04 Starboard #8 0.626 0.590 5.83 2.94 0.372 2.688 1.59 0.28 473.42 21.26

Accordingly, from the testing it is shown that the fiberboard produced according to the present application has improved heat resistance properties (e.g. RSI, heat flow rate) over gypsum boards.

Tables 3.1. 3.2 and 3.3 show results of water absorptiveness tests performed on the gypsum board samples (Table 3.1) and the fiberboard samples of the present application (Table 3.2 and 3.3), in accordance with the ASTM D3285 Standard Test Method for Water Absorptiveness of Nonbibulous Paper and Paperboard (also known as the “Cobb Test”). In table 3.1, the results of the Cobb Test for the gypsum board samples is shown, where the average absorption of the gypsum board over a 4 hour period was 773.64 g/m² and the average surface absorption was 3.24%.

TABLE 3.1 Cobb Test on 5/″ gypsum boards with water-repellent surfaces (white side) (test duration: 4 hours) Initial Final Surface Sample weight weight Absorption absorption 4 hours g g g/m² % C-1 251.57 258.05 651.91 2.51 C-2 213.40 221.81 846.08 3.79 C-3 211.93 220.52 864.19 3.90 C-4 254.97 262.25 732.40 2.78 Average 232.97 240.66 773.64 3.24

In Table 3.2, the results of the Cobb Test for the fiberboard samples of the present application is shown, where the average absorption of the fiberboard over a 2 hour period was 244.22 g/m² and the average surface absorption was 2.06%.

TABLE 3.2 Cobb Test on ⅝″ MSL fireproof and calendered fiberboard of the present application (test duration: 2 hours) Initial Final Surface Sample weight weight Absorption absorption 2 hours g g g/m² % C-1 112.25 114.51 227.37 1.97 C-2 114.79 117.03 225.35 1.91 C-3 116.41 119.06 266.60 2.23 C-4 117.76 120.32 267.55 2.13 Average 115.30 117.73 244.22 2.06

In Table 3.3, the results of the Cobb Test for the fiberboard samples of the present application is shown, where the average absorption of the fiberboard over a 4 hour period was 303.57 g/m² and the average surface absorption was 2.72%.

TABLE 3.3 Cobb Test on ⅝″ MSL fireproof and calendered fiberboard of the present application (test duration: 4 hours) Initial Final Surface Sample weight weight Absorption absorption 4 hours g g g/m² % C-1 106.60 111.79 320.93 2.85 C-2 105.59 106.66 310.87 2.84 C-3 110.94 113.59 266.60 2.33 C-4 107.50 110.64 315.90 2.84 Average 108.16 111.16 303.57 2.72

Accordingly, from the testing it is shown that the fiberboard produced according to the present application has reduced absorption properties and characteristics (absorption and surface absorption percentage) over gypsum boards.

Table 4 shows results of an absorption by water immersion test performed on the fiberboard samples of the present application, according to the ASTM C209 Standard (Standard Test Methods for Cellulosic Fiber Insulating Board—Section 14). As shown in Table 4, after a 2 hour test duration, the average absorption percentage is 6.81%.

TABLE 4 Absorption by water immersion on ⅝″ MSL fireproof and calendered fiberboard of the present application Initial Final Sample weight weight Absorption Absorption 2 hours g g g % A-1 112.40 130.68 18.28 4.96 A-2 109.71 126.57 18.86 5.12 A-3 113.92 134.95 21.03 5.70 A-4 116.16 158.48 42.32 11.48 Average 6.81

Strength tests were also performed on the fiberboard of the present application. Table 5 shows the measured results of a tensile strength test performed according to the ASTM C208 Standard (Section 13). As shown in Table 5, the tensile strength perpendicular to the surface of the fiberboard was measured, with an average net strength of: 620.67 psf, 281.53 kg and 29.72 Kpa.

TABLE 5 Tensile strength perpendicular to surface on ⅝″ MSL fireproof and calendered fiberboard of the present application Net Net Net Sample TEST TARE strength Average strength Average strength Average MIN Side # psf psf psf psf kg kg Kpa Kpa psf-kg-KPA — S-1 785 18 767 620.67 347.91 281.53 36.72 29.72 120-55-6 Bottom S-2 496 18 478 216.82 22.89 Top S-3 635 18 617 279.87 29.54 Bottom

Tables 6.1 and 6.2 show the measured results of transverse strength tests performed on the fiberboard of the present application, according to the ASTM C209 standard (Section 10). In table 6.1, the average transverse strength perpendicular to the board panel length of the “M” samples was 28.50 lbf and the average transverse strength perpendicular to the board panel length of the “T” samples was similar with 27.83 lbf. After a two week curing period, the transverse strength was measured again, and as shown in table 6.2, the average transverse strength of the “M” samples was 25.17 lbf and the average transverse strength of the “T” samples was similar with 24.70 lbf. In contrast, a gypsum board has a standard specification (according to ASTM 1.1.1) of transverse strength perpendicular to the board panel length of 23.5 lbf. Accordingly, the fiberboard of the present application has an increased transverse strength compared to gypsum board.

TABLE 6.1 Transverse strength test on ⅝″ MSL fireproof and calendered fiberboard of the present application Sample Transverse strength Average ⅝″ Starboard lbf lbf 1-M

28.50 2-M 28.2 3-M

4-M 29.8 5-M 27.8 1-T 28.0 27.83 2-T 27.6 3-T

4-T 27.7 5-T

TABLE 6.2 Transverse strength test on ⅝″ MSL fireproof and calendered fiberboard of the present application after a two week curing time Sample Transverse strength Average ⅝″ Starboard lbf lbf 1-M 25.9 25.17 2-M

3-M

4-M 24.2 5-M 25.4 1-T 23.7 24.70 2-T

3-T 25.6 4-T 24.8 5-T

Calculations were performed to determine the average density of the fiberboard of the present application. As shown in Table 7, for a fiberboard having a generally uniform ⅝″ thickness, the average dry weight was 460.94 g and the average density is 19.91 lbs/ft³.

TABLE 7 Average density calculation of the ⅝″ MSL fireproof and calendered fiberboard of the present application Sample Average Dry Natural Production thickness weight Density ⅝″ Code in g lbs/pi² 1 MSL Starboard-CA 0.6155 463.10 19.94 2 MSL Starboard-CA 0.6150 461.03 19.87 3 MSL Starboard-CA 0.5980 444.31 19.69 4 MSL Starboard-CA 0.6265 473.71 20.04 5 MSL Starboard-CA 0.6141 462.70 19.97 6 MSL Starboard-CA 0.6158 463.10 19.93 7 MSL Starboard-CA 0.6164 466.12 20.04 8 MSL Starboard-CA 0.6159 464.17 19.97 9 MSL Starboard-CA 0.6036 452.60 19.87 10 MSL Starboard-CA 0.6148 458.54 19.77 Average — 0.6135 460.94 19.91

One or more currently preferred embodiments have been described by way of example. It will be apparent to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as defined in the claims. 

What is claimed is:
 1. A fiberboard composition comprising: a plurality of ligno-cellulosic fibers; and an inorganic expandable flake graphite in an amount between 10 and 50 percent by weight for providing fire resistance.
 2. The fiberboard composition of claim 1, further comprising a waterborne polymer binder resin in a suitable amount for providing water resistance.
 3. The fiberboard composition of claim 1 further comprising a silicate for enhancing fire resistance.
 4. The fiberboard composition of claim 1, wherein said inorganic expandable graphite does not expand at temperatures less than about 240° C.
 5. The fiberboard composition of claim 2, wherein said waterborne polymer binder resin is selected from the group consisting of: latex, natural rubber, gutta-percha, styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene, polybutadiene, polychloroprenes, organic polysulphides, butyl rubber, halogenated butyl rubber, chlorinated polyethelene, chlorosulfanated polyethylene, ethylene-propoylene rubber, butadiene acrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, and all acrylic polymers.
 6. The fiberboard composition of claim 3, wherein said silicate is selected from the group consisting of: sodium silicate and potassium silicate.
 7. The fiberboard composition of claim 3, wherein said silicate contains around 10% water.
 8. A method of making a fiberboard comprising: forming a pulp slurry comprising a plurality of ligno-cellulosic fibers and water; adding of an inorganic expandable graphite to said pulp slurry for providing fire resistance to the fiberboard; pressing said pulp slurry and said inorganic expandable graphite to form at least one layer of pre-fiberboard composition; interfelting said layer of pre-fiberboard composition to form a pre-fiberboard; and drying said pre-fiberboard.
 9. The method of making a fiberboard of claim 8, further comprising adding of a waterborne polymer binder resin to said pulp slurry for providing water resistance and strength to the fiberboard.
 10. The method of making a fiberboard of claim 8, further comprising coating said pre-fiberboard with a silicate for enhancing fire resistance of said fiberboard.
 11. The method of making a fiberboard of claim 8, further comprising press rolling said pre-fiberboard to limit roughness of the fiberboard.
 12. The method of claim 8, wherein said inorganic expandable graphite does not expand at temperatures less than about 240° C.
 13. The method of claim 8, wherein said inorganic expandable graphite is added at a rate of about 10 lbs per minute.
 14. The method of claim 9, wherein the waterborne polymer binder resin is selected from a group consisting of: latex, natural rubber, gutta-percha, styrene-butadiene rubber, styrene-isoprene rubber, polyisoprene, polybutadiene, polychloroprenes, organic polysulphides, butyl rubber, halogenated butyl rubber, chlorinated polyethelene, chlorosulfanated polyethylene, ethylene-propoylene rubber, butadiene acrylonitrile copolymers, polyvinyl acetate, vinyl-acrylic, styrene-acrylic, and all acrylic polymers.
 15. The method of claim 9, wherein the waterborne polymer binder resin is added at a rate of between about 2 to about 3 gallons per minute into said pulp slurry.
 16. The method of claim 10, wherein said silicate coating is selected from the group consisting of: sodium silicate and potassium silicate.
 17. The method of claim 10, wherein said silicate coating contains around 10% water.
 18. The method of claim 11, wherein said press-rolling is performed under a temperature of between about 450 to about 500° F.
 19. The fiberboard composition of claim 1, wherein the composition comprises approximately 30% of the inorganic expandable graphite by weight.
 20. The fiberboard composition of claim 1, wherein the composition comprises approximately 15% of the inorganic expandable graphite by weight.
 21. The fiberboard composition of claim 1, wherein the composition comprises approximately 1 to 3% of the waterborne polymer binder resin. 